Micropolluants are defined as being organic or ionic chemical substances of natural or anthropic origin capable of having a toxic action at minute concentrations in a given medium. In water, these contaminants are highly varied: pesticides, steroids, polycyclic aromatic hydrocarbons (PAHs), active principles, surfactants, cosmetics, metal ions, microtoxins, bacterial toxins and the like. These pollutants are the subject of close monitoring, in particular in water intended for human consumption (Directive 98/83/CE of the Council of 3 Nov. 1998, Official Journal of the European Communities).
However, the analysis of traces of micropollutants is proving to be problematic and requires beforehand the installation of a pretreatment, followed by the use of detection techniques such as liquid chromatography coupled to detection by fluorescence, by UV-visible spectroscopy or by mass spectrometry, or gas chromatography coupled to mass spectrometry (P. Plaza-Bolaños et al., Analytical methods and trends, J. Chrom. A., 1217 (2010), 6303-6326). However, these techniques, although very efficient, can only be employed in the laboratory. In addition, they exhibit the disadvantage of requiring sometimes very long periods of time, which limits the possibilities of rapid interventions during a pollution event. The monitoring in real time, thus in situ, of these toxic agents requires the development of sensors combining miniaturization, speed, low costs and ease of use.
There exists three main categories of sensors having different transduction modes: optical, piezoelectric or electrochemical:                the optical solution, which is generally very sensitive, lends itself with difficulty to miniaturization due to a significant noise/signal ratio (X.-A. Ton et al., Biosens. Bioelec., 36 (2012), 22-28; P. Turkewitsch et al., Anal. Chem., 1998, 70, 2025-2030),        the piezoelectric route remains problematic to employ in the case of analyses in a liquid medium (C.-Y. Lin et al., Chem. Eur. J., 2003, 9, 5107-5110),        for their part, electrochemical sensors exhibit the advantage of being able to be miniaturized without loss of sensitivity due to a low noise/signal ratio. In addition, they exhibit a low production cost. However, in the case of complex matrices, it is necessary, in order to be able to analyze them, to introduce, into the electrochemical sensor, specific sites for recognizing the analyte in order to improve the detection and/or the quantification thereof; it is in this context that molecularly imprinted electrochemical sensors (V. Suryanarayanan et al., Electroanal., 22 (2010), 1795-1811) and ion imprinted electrochemical sensors (T. Prasada Rao et al., Anal. Chim. Acta, 578 (2006), 105-116) have been developed.        
The principle of printed sensors is based on the use of molecularly imprinted polymers (MIP) or of ion imprinted polymers (IIP).
The imprinted polymers are three-dimensional polymer networks prepared in the presence of a target molecule or a target ion, around which the polymer network is constructed via specific interactions between the target and a functional monomer, in the presence of a crosslinking agent. The release of the imprinted molecule or of the imprinted ion generates cavities incorporating functionalities complementary to the molecule or the ion (FIG. 1). These materials thus exhibit a high molecular or ion recognition power, their activity limiting that of biological receptors of antibody type (K. Haupt et al., Chem. Rev., 100 (2000), 2495-2504), MIPs or IIPs being more stable and easier and cheaper to manufacture than antibodies and being able to be stored for very long periods of time before use (V. Pichon, J. Chrom. A., 1152 (2007), 41-53).
Two synthetic routes can be envisaged for the preparation of molecularly or ion imprinted electrochemical sensors:                A first route in which the imprint is generated within an electrically conducting polymer devoid of crosslinking agent, the polymer having the twofold role of recognition and of transducer, the phenomenon of recognition being converted into a measurable electrical signal. This route exhibits numerous advantages and in particular ease of use, control of the thickness of the electrogenerated film and the possibility of precisely depositing the detection system on a given surface (T. L. Panasyuk et al., Anal. Chem., 71 (1999), 4609-4613). Nevertheless, their use involves the application of electrochemical measurements which can result, for example, in the entry and in the exit of counterions in the conducting polymer. These measurements detrimentally affect the imprint, in particular as a result of the noncrosslinking of the polymer network, and, eventually, the ability of the sensor to specifically track the target.        A second route in which the MIP and the transducer are separate elements. This route consists of the incorporation of particles of MIPs or IIPs, prepared and crosslinked beforehand, within a conductive phase which can be an electrically conducting polymer (K. Ho et al., Anal. Chim. Acta, 542 (2005), 90-96), or also an electrode based on carbon paste (N. Kirsch et al., Analyst., 126 (2001), 1936-1941). In this case, the risk of denaturing the imprint decreases, the disadvantage being a more difficult transmission of the information between the MIP or the IIP which has tracked the target and the conductive phase of the electrode.        
Thus, the technical problem remaining to be solved with respect to this state of the art consists of the development of a crosslinked imprinted polymer which makes possible effective transmission of the recognition phenomenon as a measurable electrical or electrochemical signal.
The technical problem of the invention lies more particularly in the development of an imprinted polymer fulfilling the role of imprinted sensor, by making it possible to directly detect a target by direct transmission of the recognition phenomenon as a measurable electrical or electrochemical signal, without it being necessary to use additional transmission means (electrochemistry, fluorescence, and the like).